We present BV photometry centered on the globular cluster M54 (NGC 6715). The color-magnitude diagram clearly shows a blue horizontal branch extending anomalously beyond the zero-age horizontal-branch theoretical models. These kinds of horizontal-branch stars (also called ``blue hook'' stars), which go beyond the lower limit of the envelope mass of

Here we report the first detection of polarization signals induced by the Zeeman effect in spectral lines of the E4Π-A4Π system of FeH located around 1.6 μm. Motivated by the tentative detection of this band in the intensity spectrum of late-type dwarfs, we have investigated the full Stokes sunspot spectrum and have found circular and linear

En esta tesis hemos estudiado una muestra de seis estrellas tipo Delta Scuti pertenecientes al cúmulo de las Pléyades observadas por medio de la red STEPHI a través de varias campañas multisitio, de las cuales dos fueron realizadas durante el desarrollo del presente trabajo. Dicha muestra consta de V650 Tau, V647 Tau, V534 Tau, V624 Tau, HD 23628 y

We present the first results of an observational project aimed at producing a database of nearby face-on spiral galaxies in the optical. The project is being run at the IAC-80 telescope in Tenerife. This first sample is made of from R and I images of NGC 428, 864, 2146, 2273, 2541, 2967, 4618, 4654, 6217, and 6643. Overall geometrical parameters

We explored the potential for use of the contractile proteins, actin and myosin, as biosensors of solutions containing mercury ions. We demonstrate that the reaction of HgCl2 with myosin rapidly inhibits actin-activated myosin ATPase activity. Mercuric ions inhibit the in vitro analog of contraction, namely the ATP-initiated superprecipitation of

Most of the spectra for the planet-host stars analyzed in this paper were studied in Papers I (Santos et al., 2000A&A...363..228S), II (Santos et al., 2001A&A...373.1019S), and III (Santos et al., 2003, Cat. . We refer the reader to these for a description of the data. During the last year, however, we have obtained spectra for 18 more planet host